This invention relates to the field of graphics display devices, and in particular to display devices capable of displaying high resolution video information.
Continuing advances in the speed and computing capability of microprocessor-based video drivers coupled with consumer demands for ever-increasing video display resolution has lead to the availability of a wide variety of video display formats for computer displays. These displays range from conventional VGA (video graphics array) resolution of 640xc3x97480 picture elements (xe2x80x9cpixelsxe2x80x9d) to SVGA (800xc3x97600 pixels); XGA (1024xc3x97768 pixels); SXGA (1280xc3x971024 pixels); all the way through to QXGA (2,048xc3x971,536 pixels), which represents a ten-fold increase in the number of pixels over a conventional VGA display. Displays with even greater resolution such as QSXGA and greater are also available or proposed. Simultaneously, consumer demands for greater resolution in home entertainment systems has lead to the selection of a 1080xc3x97720 pixel display as the standard for high definition television (HDTV).
The existence of multiple video display formats for various applications has made it desirable for a single display device to be able to accommodate various display resolutions as well as various display aspect ratios. Conventional cathode ray tube (CRT) displays have an advantage over flat panel display (FPD) devices in that a high resolution CRT can accommodate lower resolution video signals and/or video signals of different aspect ratios simply by changing the scan rate of the CRT. The disadvantages of CRT displays are their size and high power consumption, among other things. The benefits of FPDs, especially LCD-based display devices such as direct-view LCD monitors, microdisplay projectors, and microdisplay monitors include reduced space, reduced power consumption, and reduced user eye-strain. Unfortunately, because flat panel displays comprise an array of individually addressable pixels, conversion of various video display formats for display on such devices has typically required a complete microprocessor based image processing system including a video processor scaler, frame rate converter, and image optimizing software as well as one or more frame buffers to convert the input display signal into a display signal that is compatible with the particular display device. Often, complex image smoothing software must be incorporated into the system so that if a low resolution image is displayed on a high resolution display the image looks smooth without jagged image areas. Similarly, if high resolution content is displayed on a lower resolution display, data interpolation must be performed to avoid unacceptable degradation of image quality. The computing power necessary to perform these image reformatting functions at video frame rates can be quite complex and add significant cost to the overall cost of such a display system.
One possible solution to the problem of displaying information in various display formats on a given LCD-based display would be to create a display having a resolution equal to the highest resolution video format to be displayed. Video information received in a lower resolution format could be displayed by displaying a single pixel of the low-resolution video information on more than one display pixel. Unfortunately, since the various current video display formats are not integer multiples of each other (or more precisely quadruple multiples of each other) displaying course resolution information on a fine resolution display would result in clipping of the image. Alternatively, displaying course resolution information directly on a fine resolution display would result in significantly decreased image size. Accordingly, what is needed is a microdisplay having plurality of pixels that are addressable separately or in combination to permit the display to be reconfigured on-the-fly to display video information in its native format with an image size appropriate to the particular display.
The present invention comprises a flat panel display, such as a liquid crystal microdisplay having a plurality of square and rectangular pixel electrodes that are addressable separately to produce a fine resolution display or addressable in combination to create a lower resolution display. In an illustrative embodiment of the present invention, the individual pixel electrodes are arranged in a repeating macro-pixel composed of four relatively larger square pixels, eight rectangular pixels, and four relatively smaller square pixels. In a high resolution mode, each of the larger square pixels, each pair of rectangular pixels and all four of the small square pixels are addressable in groups to create the required pixels for-the fine resolution display. In the lower resolution mode, one larger square electrode in combination with two adjacent rectangular electrodes and one adjacent small square electrode are addressable as a group to create the pixels for the low resolution display. By providing sub-pixel electrodes in this precise configuration, the illustrative display is capable of displaying, for example, XGA or SXGA video data, full-size undistorted and in its native display format, thus obviating the need for expensive image processors to convert the video data from one format to another.